The present invention relates to a system for connecting a brake disc and hub, wherein the brake disc has supporting elements on an inner circumference and the brake disc hub is provided with bosses on the outer circumference. Between the brake disc hub and the brake disc, intermediate elements are distributed in the circumferential direction, which intermediate elements project into interspaces provided between the bosses and the supporting elements and ensure a transmission of the braking torque from the brake disc to the brake disc hub.
Utilizing disc brakes, a vehicle may be decelerated as a result of the conversion of kinetic energy into heat, which occurs when the brake linings come to bear frictionally against the brake disc.
During the braking operation, the brake disc, on the one hand, has to transfer circumferential forces to a wheel to which the brake disc is indirectly connected. On the other hand, the brake disc has to store frictional heat occurring during braking and discharge it into the surroundings.
The interaction of these influences may lead under high stresses to a creeping of the brake disc material and, during subsequent cooling, to surface cracks. In this case, these cracks occur particularly quickly when, as a consequence of design, a thermal expansion of the brake disc is suppressed and therefore additional thermal stresses arise.
This problem is reduced by the brake disc being separated materially from the brake disc hub to which the brake disc is fastened as a separate component. The brake disc therefore has the possibility of expanding radially under the influence of heat.
In order to achieve this, it is known to fix the brake disc radially to the brake disc hub to only a minimal extent, so that the brake disc can expand radially relatively freely under heating.
Nevertheless, cracks in the brake disc may occur, which, under certain circumstances, lead to a complete throughcrack, with the result that entire brake disc segments may break-off because the brake disc is fixed radially to only a slight extent. These parts may be thrown outward explosively, thus obviously resulting in a considerable potential for hazardous situations.
It is known from German patent document DE 103 21 795 B3 not to design the intermediate elements as bolts, but, instead, as bent sheet metal parts which, however, do not eliminate the problem described above.
German patent document DE 18 36 832 U shows, as intermediate elements, an eccentric roller arrangement as discussed above.
Furthermore, German patent document DE 100 46 705 C1, DE 101 59 799 A1, DE 199 18 069 A1 and DE 19 14 409 A provide background material regarding the disc hub connection.
A generic brake disc/hub connection is known from European patent document EP 1 384 009 B1, in which the intermediate elements consist of bolts that are seated in interspaces formed between the bosses and the supporting elements, and thus make it possible to transmit the braking torque from the brake disc to the brake disc hub.
Although, in this design, the brake disc can expand radially, there is nevertheless no safeguard which prevents parts of the brake from being thrown outward in the event of a cracking of the brake disc.
The object on which the present invention is based, therefore, is to develop further a brake disc/hub connection such that the operating reliability of the brake disc is improved.
The invention provides a system for connecting a brake disc and hub, wherein the brake disc has supporting elements on an inner circumference and the brake disc hub is provided with bosses on the outer circumference. Between the brake disc hub and the brake disc, intermediate elements are distributed in the circumferential direction, which intermediate elements project into interspaces provided between the bosses and the supporting elements and ensure a transmission of the braking torque from the brake disc to the brake disc hub. Each intermediate element bears both, secured radially by shaping, against the assigned supporting element in a depression and, secured radially by shaping, against the boss in a depression.
This design affords a brake disc/hub connection in which a dislodgement of brake disc segments, which have occurred due to a continuous crack in the brake ring, is virtually ruled out.
The intermediate elements serve, as it were, for radial securing, which hold such brake disc segments in their position and therefore maintain the functioning capacity of the brake to an extent such that no complete failure of the brake occurs. The intermediate elements thus serve for largely securing the brake disc against displacement with respect to the brake disc hub, the thermal expansion of the brake disc in relation to the brake disc hub being ensured in an operating situation in that the intermediate element bears with slight radial play against the supporting element and/or the boss.
For this purpose, provision may be made for the respective intermediate element to be covered by the assigned boss in the radial direction, in regions, at a short distance on the side otherwise facing away from the brake disc hub. The intermediate element, which, in this case, comes to bear, secured against displacement, on the supporting element of the brake disc, can travel radially according to the distance dimension in the event of the expansion of the brake disc. In principle, however, it is also contemplated to design the supporting element such that it covers the intermediate element at a short distance in the inwardly directed radial region, while it bears against the boss so as to be secured against displacement or so as likewise to be slightly movable.
In order to minimize the transmission of heat from the brake disc to the brake disc hub, the intermediate element preferably consists of a steel having low thermal conductivity, for example of stainless steel.
The intermediate element may be designed as a flat part, which is folded out of a metal sheet and which fills virtually the entire interspace present between the boss and the supporting element.
It is also contemplated, however, to design the intermediate element as a bolt, as is shown in the European patent document EP 1 384 009 B1 mentioned above.
Apart from the brake disc/bolt/brake disc hub contact regions, there is no direct contact between the supporting element and the boss. In the remaining region, the heat can be transferred only by radiation from the brake disc to the brake disc hub. This is advantageous insofar as heat transport due to radiation decreases with an increased distance between the heat-discharging part and the heat-absorbing part, that is to say, here, the width of the interspace, and is substantially lower than would be the case if there was direct contact between the structural elements.
Where very hard material is concerned, the contact region of the bolt on the supporting element or on the boss is restricted, in the most unfavorable case, to linear contact, with the result that local overloads and plastic deformations may occur. In order to prevent this from happening, the bolt should have high elastic deformability. For this purpose, the bolt may be designed as a hollow body, preferably a tubular body. The contact regions are enlarged as a result, and stresses which occur are reduced.
Preferably, the intermediate element is designed as a bolt, which is seated partially in the depression of the supporting element and partially in the depression of the boss. The intermediate element designed in this way can be produced cost-effectively and, nevertheless, ensures excellent securing of the brake disc in accordance with the invention.
Preferably, in the embodiment wherein the intermediate element is a bolt, the latter lies over a large area in a depression of the supporting element, on account of the relatively lower strength of the brake disc, as compared with a brake disc hub, so that the bolt is partially surrounded over a large area here. By contrast, the bolt comes to bear only in a partial region in a depression of the boss (or not necessarily over a large area there).
The bolt is preferably designed to be circular in cross section. It is also contemplated to design the bolt to be elliptic or to have a regular polygon in cross section.
Alternatively, the intermediate elements may take a strip form. This can be produced cost-effectively from a strip-shaped metal sheet.
Preferably, in this case, the two edges of the metal sheet which lie opposite one another are designed as thickenings, which edges delimit a surface which is depressed or “lowered” in relation to the thickenings and against which the assigned supporting element comes to bear.
In this case, furthermore, preferably, a projection is integrally formed on the side lying opposite the depressed surface and is seated in the depression, the latter being of a groove-shaped design.
Preferably, once again, the strip-shaped intermediate element consequently bears positively against the supporting element in the radial direction.
For radially securing the large-area intermediate element, too, the boss may have a depression in which a correspondingly integrally formed projection of the intermediate element is then seated, in which case both the projection and depression adapted to it may be designed such that the short covering distance between the boss and the intermediate element is obtained.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.